This invention relates generally to alpha-olefin oligomers which are useful as synthetic lubricants and functional fluids and more particularly to alpha-olefin dimer products having improved low temperature properties which can be prepared by a BF.sub.3 -promoter catalyst system using alcohol alkoxylates as promoters.
Alpha-olefin oligomers and their use as synthetic lubricants ("synlubes") are well-known. The oligomers are usually hydrogenated in order to improve their stability. Early reports of such synlubes are in Seger et al. U.S. Pat. No. 2,500,161 and Garwood U.S. Pat. No. 2,500,163. The particular applications for which such oligomer oils are used depends upon their viscosity, with viscosities of about. 2-10 cSt at 100.degree. C. being preferred for general lubricating oil applications. Low viscosity, (e.g. 1-3 cSt at 100.degree. C.) alpha-olefin dimer oils are especially useful in heat transfer, insulating, hydraulic and low temperature lubricant applications.
Co-pending application Ser. No. 554,727 describes a process for preferentially making dimer oils of linear alpha-olefins such as 1-octene and 1-decene by using a catalyst comprising boron trifluoride and an alcohol alkoxylate promoter such as 2-methoxyethanol. It has been found that this process produces dimer products which have improved low temperature properties compared to dimers prepared using other alcohol promoters such as propanol or butanol. These dimer products of 1-decene or 1-octene remain clear, without precipitation of components at -54.degree. C. The products have a unique isomer content in that they contain undetectable amounts (less than about 0.5% by weight) of, respectively, the nearly straight chain isomers 9-methylnonadecenes and 7-methylpentadecenes or, after hydrogenation of the dimer products, the saturated counterparts of these compounds. In contrast, commercially available hydrogenated dimers prepared, for example, by oligomerizing 1-decene using a BF.sub.3 -butanol, or BF.sub.3 -propanol catalyst have a significantly different isomer content than those produced using the alcohol alkoxylate promoters and contain much greater amounts (3 to 5 weight percent) of relatively linear isomers, e.g. 9-methylnonadecane, and become cloudy and exhibit significant viscosity changes at -54.degree. C.